Ethanol manufacturing process over catalyst having improved radial crush strength

ABSTRACT

Acetic acid is hydrogenation in the presence of a catalyst comprising one or more active metals on a silica support, wherein the catalyst has a radial crush strength of at least 4 N/mm. The one or more active metals may include cobalt, copper, gold, iron, nickel, palladium, platinum, iridium, osmium, rhenium, rhodium, ruthenium, tin, zinc, lanthanum, cerium, manganese, chromium, vanadium, molybdenum and mixtures thereof. Radial crush strength may be improved by steam treating the catalyst support prior to the loading of the one or more active metals.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.13/418,755, filed on Mar. 13, 2012, the entirety of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to processes for manufacturing ethanolfrom acetic acid. More specifically, the present invention relates to aprocess comprising hydrogenating acetic acid in the presence of acatalyst comprising one or more active metals on a silica support,wherein the catalyst has a radial crush strength of at least 4 N/mm. Theradial crush strength of the catalyst may be increased by streamtreating the catalyst support.

BACKGROUND OF THE INVENTION

Ethanol for industrial use is conventionally produced from organic feedstocks, such as petroleum oil, natural gas, or coal, from feed stockintermediates, such as syngas, or from starchy materials or cellulosematerials, such as corn or sugar cane. Conventional methods forproducing ethanol from organic feedstocks, as well as from cellulosematerials, include the acid-catalyzed hydration of ethylene, methanolhomologation, direct alcohol synthesis, and Fischer-Tropsch synthesis.Instability in organic feedstock prices contributes to fluctuations inthe cost of conventionally produced ethanol, making the need foralternative sources of ethanol production all the greater when feedstock prices rise. Starchy materials, as well as cellulose materials,are converted to ethanol by fermentation. However, fermentation istypically used for consumer production of ethanol, which is suitable forfuels or human consumption. In addition, fermentation of starchy orcellulose materials competes with food sources and places restraints onthe amount of ethanol that can be produced for industrial use.

Ethanol production via the reduction of alkanoic acids and/or othercarbonyl group-containing compounds has been widely studied, and avariety of combinations of catalysts, supports, and operating conditionshave been mentioned in the literature. The reduction of variouscarboxylic acids over metal oxides has been proposed by EP 0175558 andU.S. Pat. No. 4,398,039. A summary of some of the developmental effortsfor hydrogenation catalysts for conversion of various carboxylic acidsis provided in Yokoyama, et al., “Carboxylic acids and derivatives” in:Fine Chemicals Through Heterogeneous Catalysis, 2001, 370-379.

U.S. Pat. No. 6,495,730 describes a process for hydrogenating carboxylicacid using a catalyst comprising activated carbon to support activemetal species comprising ruthenium and tin. U.S. Pat. No. 6,204,417describes another process for preparing aliphatic alcohols byhydrogenating aliphatic carboxylic acids or anhydrides or esters thereofor lactones in the presence of a catalyst comprising platinum andrhenium. U.S. Pat. No. 5,149,680 describes a process for the catalytichydrogenation of carboxylic acids and their anhydrides to alcoholsand/or esters in the presence of a catalyst containing a Group VIIImetal, such as palladium, a metal capable of alloying with the GroupVIII metal, and at least one of the metals rhenium, tungsten ormolybdenum. U.S. Pat. No. 4,777,303 describes a process for theproductions of alcohols by the hydrogenation of carboxylic acids in thepresence of a catalyst that comprises a first component which is eithermolybdenum or tungsten and a second component which is a noble metal ofGroup VIII on a high surface area graphitized carbon support. U.S. Pat.No. 4,804,791 describes another process for the production of alcoholsby the hydrogenation of carboxylic acids in the presence of a catalystcomprising a noble metal of Group VIII and rhenium. U.S. Pat. No.4,517,391 describes preparing ethanol by hydrogenating acetic acid undersuperatmospheric pressure and at elevated temperatures by a processusing a predominantly cobalt-containing catalyst.

U.S. Pat. No. 7,375,049 describes a catalyst for the dehydrogenation andhydrogenation of hydrocarbons which comprises at least one first metaland at least one second metal bound to a support material. The firstmetal comprises at least one transition metal, suitably a platinum groupmetal. Tin is preferred and exemplified as the second metal. The supportmaterial must comprise an overlayer, e.g. tin oxide, such that acidicsites on the support material are substantially blocked.

Existing processes suffer from a variety of issues impeding commercialviability including: (i) catalysts without requisite selectivity toethanol; (ii) catalysts which are possibly prohibitively expensiveand/or nonselective for the formation of ethanol and that produceundesirable by-products; (iii) required operating temperatures andpressures which are excessive; and/or (iv) insufficient catalyst life.

SUMMARY OF THE INVENTION

In a first embodiment, the present invention is directed to a processfor producing ethanol, comprising hydrogenating acetic acid in a reactorin the presence of a catalyst comprising one or more active metals on asilica support, wherein the catalyst has a radial crush strength of atleast 4 N/mm, according to ASTM D6175-03. This test method is todetermine the ability of an extruded catalyst to retain physicalintegrity during use. The radial crush strength may be from 4 N/mm to 12N/mm.

In a second embodiment, the present invention is directed to a processfor producing ethanol, comprising hydrogenating acetic acid in a reactorin the presence of a catalyst comprising one or more active metals on asilica support, wherein the silica support is subjected to steamtreatment, preferably at a temperature above 50° C. for a period of timeprior to impregnating the one or more metals on the silica support. Thestream treatment may occur at a temperature from 50° C. to 300° C. for0.1 to 200 hours. After the steam treatment but prior to impregnation,the silica support, selected from the group consisting of silica,silica/alumina, calcium metasilicate, pyrogenic silica, high puritysilica and mixtures thereof, may comprise at least 0.0001% moisture. Atleast some of this moisture may be removed by subjecting the silicasupport to drying. The silica support may be present from 25 to 99 wt. %of the total catalyst and may further comprise 0.1 to 50 wt. % of asupport modifier. The active metals may include cobalt, copper, gold,iron, nickel, palladium, platinum, iridium, osmium, rhenium, rhodium,ruthenium, tin, zinc, lanthanum, cerium, manganese, chromium, vanadium,molybdenum or combinations thereof. Hydrogenation conditions include apressure of 10 to 3000 kPa and a hydrogen to acetic acid molar ratio ofgreater than 2:1. The acetic acid conversion is greater than 30% with aselectivity to ethanol of greater than 60%.

In a third embodiment, the present invention is directed to a processfor producing ethanol, comprising hydrogenating acetic acid in a reactorin the presence of a catalyst comprising silica support subjected tosteam treatment, wherein the catalyst has a radial crush strengthgreater than 50% of a radial crush strength of the silica support priorto steam treatment.

In another embodiment, the present invention is directed to a processfor producing ethanol, comprising hydrogenating acetic acid in a reactorin the presence of a catalyst comprising one or more active metals on asupport selected from the group consisting of alumina, titania,zirconia, zeolite, carbon, activated carbon, and mixtures thereof, andwherein the catalyst has a radial crush strength greater than 50% of aradial crush strength of the support prior to steam treatment.

In a fourth embodiment, the present invention is directed to ahydrogenation catalyst for converting acetic acid to ethanol, thecatalyst comprising: one or more active metals on a silica support,wherein the one or more active metals is selected from the groupconsisting of cobalt, copper, gold, iron, nickel, palladium, platinum,iridium, osmium, rhenium, rhodium, ruthenium, tin, zinc, lanthanum,cerium, manganese, chromium, vanadium, molybdenum and mixtures thereof,wherein the catalyst has a radial crush strength of at least 4 N/mm. Thesilica support may be subjected to stream treatment at a temperatureabove 50° C. for a period of time prior to impregnating the one or moremetals on the silica support.

In a fifth embodiment, the present invention is directed to a processfor making a catalyst for hydrogenating acetic acid having increasedradial crush strength, comprising providing a dry support selected fromthe group consisting of silica, silica/alumina, calcium metasilicate,pyrogenic silica, high purity silica, and mixtures thereof; subjectingthe dry support to treatment with steam at a temperature from 50° C. to300° C. for a period of time from 0.1 to 200 hours; drying the supportsuch that the support comprises at least 0.5% moisture after treatment;and impregnating the support with the one or more active metals. Thecatalyst may further be calcined at a temperature from 250° C. to 800°C., optionally for a period from 1 to 12 hours.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to processes for producing ethanol thatcomprise hydrogenating acetic acid and hydrogen in a reactor in thepresence of a catalyst comprising one or more active metals or oxidesthereof on a silica support, wherein the catalyst has a radial crushstrength of at least 4 N/mm. In producing ethanol from hydrogenatingacetic acid, it is desirable to use a catalyst that can withstand a highmass flow rate, pressure drop, and/or weight load in the hydrogenationreactor, but which also can be manufactured economically. Many plantshutdowns occur due to the mechanical failure of the catalyst, such asincreases in pressure drop in axial reactors or bypass formation inradial reactors, rather than low catalytic activity. Decreases in radialcrush strength may occur due to cracks in the support.

Embodiments of the present invention overcome this problem by usingsupports, such as silica supports, which have been pre-treated tomaintain a high radial crush strength for the catalyst despite metalimpregnation using a metal/water solution. In one embodiment, thepresent invention is directed to a process for producing ethanol,comprising hydrogenating acetic acid in a reactor in the presence of acatalyst comprising one or more active metals on a silica support,wherein the silica support is subjected to steam treatment at atemperature above 50° C. for a period of time prior to impregnating theone or more metals on the silica support. In another embodiment, thepresent invention is directed to a process for producing ethanol,comprising hydrogenating acetic acid in a reactor in the presence of acatalyst comprising a silica support subjected to steam treatment,wherein the catalyst has a radial crush strength greater than 50% of acrush strength of the silica support prior to steam treatment.

The catalyst of the present invention preferably has a radial crushstrength of at least 4 N/mm, e.g., at least 5 N/mm, or at least 7.5N/mm. In one embodiment, the catalyst has a radial crush strength from 4N/mm to 12 N/mm. In another embodiment, the catalyst has a radial crushstrength greater than 50% of the radial crush strength of the silicasupport prior to steam treatment. For example, if the dry silica supportprior to steam treatment or impregnation has a radial crush strength of10 N/mm, then the catalyst of the present invention has a radial crushstrength greater than 5 N/mm.

The catalyst composition for use in the present invention comprises asilica support. In preferred embodiments, the support material ispresent in an amount from 25 wt. % to 99 wt. %, e.g., from 30 wt. % to98 wt. % or from 35 wt. % to 95 wt. %, based on the total weight of thecatalyst composition. The silica support may be selected from the groupconsisting of silica, silica/alumina, pyrogenic silica, high puritysilica, and mixtures thereof. In general silica supports have lowerradial crush strength than other types of supports, thus steam treatmentis useful in increasing the radial crush strength of silica supportedcatalysts. However, steam treatment may also be used for other supports,such as alumina, titania, zirconia, zeolite, carbon, activated carbon,and mixtures thereof.

The surface area of the silica support preferably is at least 50 m²/g,e.g., at least 100 m²/g, at least 150 m²/g, at least 200 m²/g or mostpreferably at least 250 m²/g. In terms of ranges, the silica supportpreferably has a surface area from 50 to 600 m²/g, e.g., from 100 to 500m²/g or from 100 to 300 m²/g. For the purposes of the presentspecification, surface area refers to BET nitrogen surface area, meaningthe surface area as determined by ASTM D6556-04, the entirety of whichis incorporated herein by reference.

The silica support also preferably has an average pore diameter from 5to 100 nm, e.g., from 5 to 30 nm, from 5 to 25 nm or from 5 to 10 nm, asdetermined by mercury intrusion porosimetry, and an average pore volumefrom 0.5 to 2.0 cm³/g, e.g., from 0.7 to 1.5 cm³/g or from 0.8 to 1.3cm³/g, as determined by mercury intrusion porosimetry.

The morphology of the silica support, and hence of the catalystcomposition for use herein, may vary widely. In some exampleembodiments, the morphology of the support and/or of the catalyst may bepellets, extrudates, spheres, spray dried microspheres, rings,pentarings, trilobes, quadrilobes, multi-lobal shapes, or flakesalthough cylindrical pellets are preferred. Preferably, the support hasa morphology that allows for a packing density from 0.1 to 1.0 g/cm³,e.g., from 0.2 to 0.9 g/cm³ or from 0.3 to 0.8 g/cm³. In terms of size,the support preferably has an average particle size, e.g., meaning thediameter for spherical particles or equivalent spherical diameter fornon-spherical particles, from 0.01 to 1.0 cm, e.g., from 0.1 to 0.5 cmor from 0.2 to 0.4 cm. Since the one or more active metal(s) that aredisposed on or within the support are generally very small in size,those active metals should not substantially impact the size of theoverall catalyst particles. Thus, the above particle sizes generallyapply to both the size of the support as well as the final catalystparticles.

In some embodiments, the support material may also comprise a supportmodifier. A support modifier may adjust the acidity of the supportmaterial. In one embodiment, support modifiers are present in an amountfrom 0.1 to 50 wt. %, e.g., from 0.2 to 25 wt. %, from 0.5 to 15 wt. %,or from 1 to 8 wt. %, based on the total weight of the catalystcomposition.

For example, the acid sites, e.g. Brønsted acid sites, on the supportmaterial may be adjusted by the support modifier to favor selectivity toethanol during the hydrogenation of acetic acid. The acidity of thesupport material may be adjusted by reducing the number or reducing theavailability of Brønsted acid sites on the support material. The supportmaterial may also be adjusted by having the support modifier change thepKa of the support material. Unless the context indicates otherwise, theacidity of a surface or the number of acid sites thereupon may bedetermined by the technique described in F. Delannay, Ed.,“Characterization of Heterogeneous Catalysts”; Chapter III: Measurementof Acidity of Surfaces, p. 370-404; Marcel Dekker, Inc., N.Y. 1984, theentirety of which is incorporated herein by reference. In particular,the use of a modified support that adjusts the acidity of the support tomake the support less acidic or more basic favors formation of ethanolover other hydrogenation products.

In some embodiments, the support modifier may be an acidic modifier thatincreases the acidity of the catalyst. Suitable acidic support modifiersmay be selected from the group consisting of: oxides of Group IVBmetals, oxides of Group VB metals, oxides of Group VIB metals, oxides ofGroup VIIB metals, oxides of Group VIII metals, aluminum oxides, andmixtures thereof. Acidic support modifiers include those selected fromthe group consisting of ZrO₂, Nb₂O₅, Ta₂O₅, Al₂O₃, B₂O₃, P₂O₅, andSb₂O₃. The acidic modifier may also include those selected from thegroup consisting of WO₃, MoO₃, Fe₂O₃, Cr₂O₃, V₂O₅, MnO₂, CuO, Co₂O₃, andBi₂O₃. Preferred acidic support modifiers include those selected fromthe group consisting of WO₃, MoO₃, ZrO₂, Nb₂O₅, Ta₂O₅, and Al₂O₃.

In another embodiment, the support modifier may be a basic modifier thathas a low volatility or no volatility. Such basic modifiers, forexample, may be selected from the group consisting of: (i) alkalineearth metal oxides, (ii) alkali metal oxides, (iii) alkaline earth metalmetasilicates, (iv) alkali metal metasilicates, (v) Group IIB metaloxides, (vi) Group IIB metal metasilicates, (vii) Group IIIB metaloxides, (viii) Group IIIB metal metasilicates, and mixtures thereof. Inaddition to oxides and metasilicates, other types of modifiers includingnitrates, nitrites, acetates, and lactates may be used. Preferably, thesupport modifier is selected from the group consisting of oxides andmetasilicates of any of sodium, potassium, magnesium, calcium, scandium,yttrium, and zinc, as well as mixtures of any of the foregoing. Morepreferably, the basic support modifier is a calcium silicate, and evenmore preferably calcium metasilicate (CaSiO₃) or calcium oxide (CaO).When the basic support modifier comprises calcium metasilicate, in someembodiments, at least a portion of the calcium metasilicate may be incrystalline form.

The catalysts of the invention preferably include one or more activemetals or oxides thereof. The one or more active metals are selectedfrom the group consisting of cobalt, copper, gold, iron, nickel,palladium, platinum, iridium, osmium, rhenium, rhodium, ruthenium, tin,zinc, lanthanum, cerium, manganese, chromium, vanadium, and molybdenum.The total metal loading of the one or more active metals is from 0.1 to25 wt. %, e.g., from 0.5 to 20 wt. %. or from 0.6 to 15 wt. %. In oneembodiment, the one or more active metals may include a precious metalthat is selected from the group consisting of rhodium, rhenium,ruthenium, platinum, palladium, osmium, iridium and gold. The preciousmetal may be in elemental form or in molecular form, e.g., an oxide ofthe precious metal. It is preferred that the catalyst comprises suchprecious metals in an amount less than 5 wt. %, e.g., less than 3 wt. %,less than 1 wt. % or less than 0.5 wt. %. In terms of ranges, thecatalyst may comprise the precious metal in an amount from 0.05 to 10wt. %, e.g. from 0.1 to 5 wt. %, or from 0.1 to 3 wt. %, based on thetotal weight of the catalyst.

In another embodiment, the catalyst may comprise two active metals orthree active metals. The first metal or oxides thereof may be selectedfrom the group consisting of cobalt, rhodium, rhenium, ruthenium,platinum, palladium, osmium, iridium and gold. The second metal oroxides thereof may be selected from the group consisting of copper,iron, tin, cobalt, nickel, zinc, and molybdenum. The third metal oroxides thereof, if present, may be selected from the group consisting ofcopper, molybdenum, tin, chromium, iron, cobalt, vanadium, palladium,platinum, lanthanum, cerium, manganese, ruthenium, rhenium, gold, andnickel. Preferably, the third metal is different than the first metaland the second metal. In addition, the first metal and the second metalmay be different, and the third metal and the second metal may bedifferent.

The metal loadings of the first, second, and optionally third metals areas follows. The first active metal may be present in the catalyst in anamount from 0.05 to 20 wt. %, e.g. from 0.1 to 10 wt. %, or from 0.5 to5 wt. %. The second active metal may be present in an amount from 0.05to 20 wt. %, e.g., from 0.1 to 10 wt. %, or from 0.5 to 8 wt. %. If thecatalyst further comprises a third active metal, the third active metalmay be present in an amount from 0.05 to 20 wt. %, e.g., from 0.05 to 10wt. %, or from 0.5 to 8 wt. %. The active metals may be alloyed with oneanother or may comprise a non-alloyed metal solution, a metal mixture orbe present as one or more metal oxides. For purposes of the presentspecification, unless otherwise indicated, weight percent is based onthe total weight the catalyst including metal and support.

Bimetallic catalysts for some exemplary catalyst compositions, excludingcesium and tungsten on the support, include platinum/tin,platinum/ruthenium, platinum/rhenium, platinum/cobalt, platinum/nickel,palladium/ruthenium, palladium/rhenium, palladium/cobalt,palladium/copper, palladium/nickel, ruthenium/cobalt, gold/palladium,ruthenium/rhenium, ruthenium/iron, rhodium/iron, rhodium/cobalt,rhodium/nickel, cobalt/tin, and rhodium/tin. More preferred bimetalliccatalysts include platinum/tin, platinum/cobalt, platinum/nickel,palladium/cobalt, palladium/copper, palladium/nickel, ruthenium/cobalt,ruthenium/iron, rhodium/iron, rhodium/cobalt, rhodium/nickel,cobalt/tin, and rhodium/tin.

In some embodiments, the catalyst may be a ternary catalyst thatcomprises three active metals on a support. Exemplary ternary catalysts,may include palladium/tin/rhenium, palladium/cobalt/rhenium,palladium/nickel/rhenium, palladium/cobalt/tin, platinum/tin/palladium,platinum/tin/rhodium, platinum/tin/gold, platinum/tin/iridium,platinum/cobalt/tin, platinum/tin/chromium, platinum/tin/copper,platinum/tin/zinc, platinum/tin/nickel, rhodium/nickel/tin,rhodium/cobalt/tin and rhodium/iron/tin. More preferably, a ternarycatalyst comprises three active metals may include palladium/cobalt/tin,platinum/tin/palladium, platinum/cobalt/tin, platinum/tin/chromium,platinum/tin/copper, platinum/tin/nickel, rhodium/nickel/tin,rhodium/cobalt/tin and rhodium/iron/tin.

Preferably, one or more of the active metals is selected from the GroupVIII metals. The Group VIII metal may be selected from the groupconsisting of iron, cobalt, nickel, ruthenium, rhodium, platinum,palladium, osmium, iridium and combinations thereof. Additional activemetals may also be used in some embodiments. Therefore, non-limitingexamples of active metals on the present catalyst composition withcesium include platinum/tin/cesium, palladium/tin/cesium,platinum/palladium/tin/cesium, nickel/tin/cesium,platinum/nickel/tin/cesium, iron/platinum/tin/cesium, etc. The activemetals may be alloyed with one another or may comprise non-alloyed metalsolutions or mixtures.

Process for Making Catalyst

In one embodiment of making the catalyst for use herein, one or moresupport modifiers, if desired, may be added to the support by mixing orthrough impregnation. Powdered materials of the modified support or aprecursor thereto may be pelletized, crushed and sieved. Drying may alsobe preformed after the support modifier is added.

The modified or unmodified support chosen for the catalyst compositionmay be shaped into particles having the desired size distribution, e.g.,to form particles having an average particle size in the range from 0.2to 0.4 cm. The support may be extruded, pelletized, tabletized, pressed,crushed or sieved to the desired size distribution. Any of the knownmethods to shape the support material into desired size distribution canbe employed.

In a preferred method of preparing the catalyst, the dry silica supportis subjected to a steam treatment prior to impregnation with the one ormore active metals. Preferably, the steam treatment may be carried outat a temperature from 50° C. to 300° C., e.g., from 50° C. to 150° C. orfrom 50° C. to 80° C. Preferably, the catalyst is subjected to steamtreatment from 0.1 to 200 hours. The steam treatment may be carried outat a partial pressure from 100 to 5,000 kPa. The weight of the silicasupport may increase by at least 0.0001% during steam treatment.Preferably, the weight of the silica support may increase by at least 5during steam treatment, e.g., by at least 20%, by at least 25%, or by atleast 33%.

In one embodiment, the extra moisture content of the steam treatedsilica support may be removed through evaporation. Moisture in the steamtreated silica support may be evaporated under reduced pressure to reachthe desired level of moisture. Alternatively, the amount of steamtreatment may be controlled such that the desired level of moisture isadded without the need for evaporation. Preferably, the moisture contentin the steam treated silica support is reduced by at least 50% beforethe active metals are impregnated. In one exemplary embodiment, radialcrush strength remains the same as initial support when the catalystcontains up to 33% moisture.

In a preferred method of preparing the catalyst, the active metals areimpregnated onto the modified or unmodified steam treated silicasupport. A precursor of the active metal preferably is used in the metalimpregnation step, such as a water soluble compound or water dispersiblecompound/complex that includes the active metal. Depending on the metalprecursor employed, the use of a solvent, such as water, glacial aceticacid or an organic solvent may be preferred. The next active metal alsopreferably is impregnated into the support material from a next metalprecursor, and so forth. If desired, additional metal precursors mayalso be impregnated into the support material.

Impregnation occurs by adding, optionally drop wise or spray, any or allthe metal precursors, preferably in suspension or solution, to the steamtreated silica support. The resulting mixture may then be heated,optionally under vacuum, in order to remove the solvent. Additionaldrying and calcining may then be performed, optionally with rampedheating, to form the final catalyst composition. Upon heating and/or theapplication of vacuum, the metals of the metal precursors preferablydecompose into their elemental (or oxide) form. In some cases, thecompletion of removal of the liquid carrier, e.g., water, may not takeplace until the catalyst is placed into use and calcined, e.g.,subjected to the high temperatures encountered during operation. Duringthe calcination step, or at least during the initial phase of use of thecatalyst, such compounds are converted into a catalytically active formof the metal or a catalytically active oxide thereof.

Impregnation of the active metals (and optional additional metals) intothe support may occur simultaneously (co-impregnation) or sequentially.In simultaneous impregnation, the metal precursors (and optionallyadditional metal precursors) are mixed together and added to the supportmaterial together, followed by drying and calcination to form the finalcatalyst composition. With simultaneous impregnation, it may be desiredto employ a dispersion agent, surfactant, or solubilizing agent, e.g.,ammonium oxalate, to facilitate the dispersing or solubilizing of theactive metal precursors in the event the two precursors are incompatiblewith the desired solvent, e.g., water.

In sequential impregnation, the first metal precursor is first added tothe support material followed by drying and calcining, and the resultingmaterial is then impregnated with the next metal precursor followed byan additional drying and calcining step to form the final catalystcomposition. Additional metal precursors may be added either with thefirst and/or next metal precursor or a separate third impregnation step,followed by drying and calcination. Combinations of sequential andsimultaneous impregnation may be employed if desired.

Suitable metal precursors include, for example, metal halides, aminesolubilized metal hydroxides, metal nitrates or metal oxalates. Forexample, suitable compounds for platinum precursors and palladiumprecursors include chloroplatinic acid, ammonium chloroplatinate, aminesolubilized platinum hydroxide, platinum nitrate, platinum ammoniumnitrate, platinum tetra ammonium nitrate, platinum chloride, platinumoxalate, palladium nitrate, palladium tetra ammonium nitrate, palladiumchloride, palladium oxalate, sodium palladium chloride, and sodiumplatinum chloride. A suitable tin precursor is stannous oxalate,stannous chloride, and stannic chloride. Generally, both from the pointof view of economics and environmental aspects, aqueous solutions ofsoluble compounds of platinum are preferred. A particularly preferredprecursor to platinum is platinum oxalate. Calcining of the solutionwith the support and active metal may occur, for example, at atemperature from 250° C. to 800° C., e.g., from 300° C. to 700° C. orfrom 500° C. to 550° C., optionally for a period from 1 to 12 hours,e.g., from 2 to 10 hours, from 4 to 8 hours or 6 hours.

Process for Hydrogenating Acetic Acid

One advantage of the catalyst for use in the present invention is thestability or activity of the catalyst for producing ethanol.Accordingly, it can be appreciated that the catalyst for use in thepresent invention is fully capable of being used in commercial scaleindustrial applications for hydrogenation of acetic acid, particularlyin the production of ethanol. In particular, it is possible to achieve adegree of stability such that catalyst activity will have a rate ofproductivity decline that is less than 6% per 100 hours of catalystusage, e.g., less than 3% per 100 hours or less than 1.5% per 100 hours.Preferably, the rate of productivity decline is determined once thecatalyst has achieved steady-state conditions.

The raw materials, e.g. acetic acid and hydrogen, fed to the reactionzone used in connection with the process of this invention may bederived from any suitable source including natural gas, petroleum, coal,biomass, and so forth. As examples, acetic acid may be produced viamethanol carbonylation, acetaldehyde oxidation, ethylene oxidation,oxidative fermentation, and anaerobic fermentation. Methanolcarbonylation processes suitable for production of acetic acid aredescribed in U.S. Pat. Nos. 7,208,624; 7,115,772; 7,005,541; 6,657,078;6,627,770; 6,143,930; 5,599,976; 5,144,068; 5,026,908; 5,001,259; and4,994,608, the entire disclosures of which are incorporated herein byreference. Optionally, the production of ethanol and ethyl acetate maybe integrated with such processes.

As petroleum and natural gas prices fluctuate becoming either more orless expensive, methods for producing acetic acid and intermediates suchas methanol and carbon monoxide from alternate carbon sources have drawnincreasing interest. In particular, when petroleum is relativelyexpensive, it may become advantageous to produce acetic acid fromsynthesis gas (“syngas”) that is derived from more available carbonsources. U.S. Pat. No. 6,232,352, the entirety of which is incorporatedherein by reference, for example, teaches a method of retrofitting amethanol plant for the manufacture of acetic acid. By retrofitting amethanol plant, the large capital costs associated with CO generationfor a new acetic acid plant are significantly reduced or largelyeliminated. All or part of the syngas is diverted from the methanolsynthesis loop and supplied to a separator unit to recover CO, which isthen used to produce acetic acid. In a similar manner, hydrogen for thehydrogenation step may be supplied from syngas.

In some embodiments, some or all of the raw materials for theabove-described acetic acid hydrogenation process may be derivedpartially or entirely from syngas. For example, the acetic acid may beformed from methanol and carbon monoxide, both of which may be derivedfrom syngas. The syngas may be formed by partial oxidation reforming orsteam reforming, and the carbon monoxide may be separated from syngas.Similarly, hydrogen that is used in the step of hydrogenating the aceticacid to form the crude ethanol product may be separated from syngas. Thesyngas, in turn, may be derived from variety of carbon sources. Thecarbon source, for example, may be selected from the group consisting ofnatural gas, oil, petroleum, coal, biomass, and combinations thereof.Syngas or hydrogen may also be obtained from bio-derived methane gas,such as bio-derived methane gas produced by landfills or agriculturalwaste.

In another embodiment, the acetic acid used in the hydrogenation stepmay be formed from the fermentation of biomass. The fermentation processpreferably utilizes an acetogenic process or a homoacetogenicmicroorganism to ferment sugars to acetic acid producing little, if any,carbon dioxide as a by-product. The carbon efficiency for thefermentation process preferably is greater than 70%, greater than 80% orgreater than 90% as compared to conventional yeast processing, whichtypically has a carbon efficiency of about 67%. Optionally, themicroorganism employed in the fermentation process is of a genusselected from the group consisting of Clostridium, Lactobacillus,Moorella, Thermoanaerobacter, Propionibacterium, Propionispera,Anaerobiospirillum, and Bacteriodes, and in particular, species selectedfrom the group consisting of Clostridium formicoaceticum, Clostridiumbutyricum, Moorella thermoacetica, Thermoanaerobacter kivui,Lactobacillus delbrukii, Propionibacterium acidipropionici,Propionispera arboris, Anaerobiospirillum succinicproducens, Bacteriodesamylophilus and Bacteriodes ruminicola. Optionally in this process, allor a portion of the unfermented residue from the biomass, e.g. lignans,may be gasified to form hydrogen that may be used in the hydrogenationstep of the present invention. Exemplary fermentation processes forforming acetic acid are disclosed in U.S. Pat. Nos. 6,509,180;6,927,048; 7,074,603; 7,507,562; 7,351,559; 7,601,865; 7,682,812; and7,888,082, the entireties of which are incorporated herein by reference.See also U.S. Pub. Nos. 2008/0193989 and 2009/0281354, the entireties ofwhich are incorporated herein by reference.

Examples of biomass include, but are not limited to, agriculturalwastes, forest products, grasses, and other cellulosic material, timberharvesting residues, softwood chips, hardwood chips, tree branches, treestumps, leaves, bark, sawdust, off-spec paper pulp, corn, corn stover,wheat straw, rice straw, sugarcane bagasse, switchgrass, miscanthus,animal manure, municipal garbage, municipal sewage, commercial waste,grape pumice, almond shells, pecan shells, coconut shells, coffeegrounds, grass pellets, hay pellets, wood pellets, cardboard, paper,plastic, and cloth. See, e.g., U.S. Pat. No. 7,884,253, the entirety ofwhich is incorporated herein by reference. Another biomass source isblack liquor, a thick, dark liquid that is a byproduct of the Kraftprocess for transforming wood into pulp, which is then dried to makepaper. Black liquor is an aqueous solution of lignin residues,hemicellulose, and inorganic chemicals.

U.S. Pat. No. RE 35,377, incorporated herein by reference, provides amethod for the production of methanol by conversion of carbonaceousmaterials such as oil, coal, natural gas and biomass materials. Theprocess includes hydrogasification of solid and/or liquid carbonaceousmaterials to obtain a process gas which is steam pyrolized withadditional natural gas to form synthesis gas. The syngas is converted tomethanol which may be carbonylated to acetic acid. The method likewiseproduces hydrogen which may be used in connection with this invention asnoted above. U.S. Pat. No. 5,821,111, which discloses a process forconverting waste biomass through gasification into synthesis gas, andU.S. Pat. No. 6,685,754, which discloses a method for the production ofa hydrogen-containing gas composition, such as a synthesis gas includinghydrogen and carbon monoxide, are incorporated herein by reference intheir entireties.

The acetic acid feedstock fed to the hydrogenation reaction zone mayalso comprise other carboxylic acids and anhydrides, as well as aldehydeand/or ketones, such as acetaldehyde and acetone. Preferably, a suitableacetic acid feed stream comprises one or more of the compounds selectedfrom the group consisting of acetic acid, acetic anhydride,acetaldehyde, ethyl acetate, and mixtures thereof. These other compoundsmay also be hydrogenated in the processes of the present invention. Insome embodiments, the presence of carboxylic acids, such as propanoicacid or its anhydride, may be beneficial in producing propanol. Watermay also be present in the acetic acid feed.

Alternatively, acetic acid in vapor form may be taken directly as crudeproduct from the flash vessel of a methanol carbonylation unit of theclass described in U.S. Pat. No. 6,657,078, the entirety of which isincorporated herein by reference. The crude vapor product, for example,may be fed directly to the hydrogenation reactor without the need forcondensing the acetic acid and light ends or removing water, savingoverall processing costs.

The acetic acid may be vaporized at the reaction temperature, followingwhich the vaporized acetic acid may be fed along with hydrogen in anundiluted state or diluted with a relatively inert carrier gas, such asnitrogen, argon, helium, carbon dioxide and the like. For reactions runin the vapor phase, the temperature should be controlled in the systemsuch that it does not fall below the dew point of acetic acid. In oneembodiment, the acetic acid may be vaporized at the boiling point ofacetic acid at the particular pressure, and then the vaporized aceticacid may be further heated to the reactor inlet temperature. In anotherembodiment, the acetic acid is mixed with other gases before vaporizing,followed by heating the mixed vapors up to the reactor inlettemperature. Preferably, the acetic acid is transferred to the vaporstate by passing hydrogen and/or recycle gas through the acetic acid ata temperature at or below 150° C., followed by heating of the combinedgaseous stream to the reactor inlet temperature.

The reaction zone, in some embodiments, may include a variety ofconfigurations using a fixed bed reactor or a fluidized bed reactor. Inmany embodiments of the present invention, an “adiabatic” reactor can beused; that is, there is little or no need for internal plumbing throughthe reaction zone to add or remove heat. In other embodiments, a radialflow reactor or reactors may be employed as the reactor, or a series ofreactors may be employed with or without heat exchange, quenching, orintroduction of additional feed material. Alternatively, a shell andtube reactor provided with a heat transfer medium may be used. In manycases, the reaction zone may be housed in a single vessel or in a seriesof vessels with heat exchangers therebetween.

In preferred embodiments, the catalyst is employed in a fixed bedreactor, e.g., in the shape of a pipe or tube, where the reactants,typically in the vapor form, are passed over or through the catalyst.Other reactors, such as fluid or ebullient bed reactors, can beemployed. In some instances, the hydrogenation catalyst may be used inconjunction with an inert material to regulate the pressure drop of thereactant stream through the catalyst bed and the contact time of thereactant compounds with the catalyst particles.

The hydrogenation in the reactor may be carried out in either liquidphase or vapor phase. Preferably, the reaction is carried out in thevapor phase under the following conditions. The reaction temperature mayrange from 125° C. to 350° C., e.g., from 200° C. to 325° C., from 225°C. to 300° C., or from 250° C. to 300° C. The pressure may range from 10kPa to 3000 kPa, e.g., from 50 kPa to 2500 kPa, or from 100 kPa to 2250kPa. The reactants may be fed to the reactor at a gas hourly spacevelocity (GHSV) of greater than 500 hr⁻¹, e.g., greater than 1000 hr⁻¹,greater than 2500 hr⁻¹ or even greater than 5000 hr⁻¹. In terms ofranges the GHSV may range from 500 hr⁻¹ to 50,000 hr⁻¹, e.g., from 500hr⁻¹ to 30,000 hr⁻¹, from 1000 hr⁻¹ to 10,000 hr⁻¹, or from 1000 hr⁻¹ to6500 hr⁻¹.

The hydrogenation optionally is carried out at a pressure justsufficient to overcome the pressure drop across the catalyst bed at theGHSV selected, although there is no bar to the use of higher pressures,it being understood that considerable pressure drop through the reactorbed may be experienced at high space velocities, e.g., 5000 hr⁻¹ or6,500 hr⁻¹.

Although the reaction consumes two moles of hydrogen per mole of aceticacid to produce one mole of ethanol, the actual molar ratio of hydrogento acetic acid in the feed stream may vary from 100:1 to 1:100, e.g.,from 50:1 to 1:50, from 20:1 to 1:2, or from 12:1 to 1:1. Mostpreferably, the molar ratio of hydrogen to acetic acid is greater than2:1, e.g., greater than 4:1 or greater than 8:1. Generally, the reactormay use an excess of hydrogen, while a secondary hydrogenation reactormay use a sufficient amount of hydrogen as necessary to hydrogenate theimpurities. In one aspect, a portion of the excess hydrogen from thereactor is directed to a secondary reactor for hydrogenation. In someoptional embodiments, a secondary reactor could be operated at a higherpressure than the hydrogenation reactor and a high pressure gas streamcomprising hydrogen may be separated from such secondary reactor liquidproduct in an adiabatic pressure reduction vessel, and the gas streamcould be directed to the hydrogenation reactor system.

Contact or residence time can also vary widely, depending upon suchvariables as amount of acetic acid, catalyst, reactor, temperature, andpressure. Typical contact times range from a fraction of a second tomore than several hours when a catalyst system other than a fixed bed isused, with preferred contact times, at least for vapor phase reactions,from 0.1 to 100 seconds, e.g., from 0.3 to 80 seconds or from 0.4 to 30seconds.

For purposes of the present invention, the term “conversion” refers tothe amount of acetic acid in the feed that is converted to a compoundother than acetic acid. Conversion is expressed as a percentage based onacetic acid in the feed. The conversion may be at least 30%, e.g., atleast 40%, or at least 60%. As stated above, the conversion withsequentially prepared catalyst is greater than the conversion with asimultaneously prepared catalyst. Although catalysts that have highconversions are desirable, such as at least 60%, in some embodiments alow conversion may be acceptable at high selectivity for ethanol. It is,of course, well understood that in many cases, it is possible tocompensate for conversion by appropriate recycle streams or use oflarger reactors, but it is more difficult to compensate for poorselectivity.

Selectivity is expressed as a mole percent based on converted aceticacid. It should be understood that each compound converted from aceticacid has an independent selectivity and that selectivity is independentfrom conversion. For example, if 60 mol. % of the converted acetic acidis converted to ethanol, we refer to the ethanol selectivity as 60%.Preferred embodiments of the hydrogenation process also have lowselectivity to undesirable products, such as methane, ethane, and carbondioxide. The selectivity to these undesirable products preferably isless than 4%, e.g., less than 2% or less than 1%. More preferably, theseundesirable products are present in undetectable amounts. Formation ofalkanes may be low, and ideally less than 2%, less than 1%, or less than0.5% of the acetic acid passed over the catalyst is converted toalkanes, which have little value other than as fuel.

The term “productivity,” as used herein, refers to the grams of aspecified product, e.g., ethanol, formed during the hydrogenation basedon the kilograms of catalyst used per hour. In terms of ethanol, forexample, a productivity of at least 100 grams of ethanol per kilogram ofcatalyst per hour, e.g., at least 400 grams of ethanol per kilogram ofcatalyst per hour or at least 600 grams of ethanol per kilogram ofcatalyst per hour, is preferred. In terms of ranges, the productivitypreferably is from 100 to 3,000 grams of ethanol per kilogram ofcatalyst per hour, e.g., from 400 to 2,500 grams of ethanol per kilogramof catalyst per hour or from 600 to 2,000 grams of ethanol per kilogramof catalyst per hour.

Ethanol may be recovered from the product produced by the presentprocess using suitable separation techniques.

The ethanol separated from the product of the process may be anindustrial grade ethanol comprising from 75 to 96 wt. % ethanol, e.g.,from 80 to 96 wt. % or from 85 to 96 wt. % ethanol, based on the totalweight of the ethanol product. In some embodiments, when further waterseparation is used, the ethanol product preferably contains ethanol inan amount that is greater than 97 wt. %, e.g., greater than 98 wt. % orgreater than 99.5 wt. %. The ethanol product in this aspect preferablycomprises less than 3 wt. % water, e.g., less than 2 wt. % or less than0.5 wt. %.

The ethanol produced by the embodiments of the present invention may beused in a variety of applications including fuels, solvents, chemicalfeedstocks, pharmaceutical products, cleansers, sanitizers,hydrogenation transport or consumption. In fuel applications, theethanol may be blended with gasoline for motor vehicles such asautomobiles, boats and small piston engine aircraft. In non-fuelapplications, the ethanol may be used as a solvent for toiletry andcosmetic preparations, detergents, disinfectants, coatings, inks, andpharmaceuticals. The ethanol and ethyl acetate may also be used as aprocessing solvent in manufacturing processes for medicinal products,food preparations, dyes, photochemicals and latex processing.

The ethanol may also be used as a chemical feedstock to make otherchemicals such as vinegar, ethyl acrylate, ethyl acetate, ethylene,glycol ethers, ethylamines, ethyl benzene, aldehydes, butadiene, andhigher alcohols, especially butanol. In the production of ethyl acetate,the ethanol may be esterified with acetic acid. In another application,the ethanol may be dehydrated to produce ethylene. Any known dehydrationcatalyst can be employed to dehydrate ethanol, such as those describedin copending U.S. Pub. Nos. 2010/0030002 and 2010/0030001, the entirecontents and disclosures of which are hereby incorporated by reference.A zeolite catalyst, for example, may be employed as the dehydrationcatalyst. Preferably, the zeolite has a pore diameter of at least 0.6nm, and preferred zeolites include dehydration catalysts selected fromthe group consisting of mordenite, ZSM-5, a zeolite X and a zeolite Y.Zeolite X is described, for example, in U.S. Pat. No. 2,882,244 andzeolite Y in U.S. Pat. No. 3,130,007, the entireties of which are herebyincorporated herein by reference.

The following examples describe the catalysts and processes of thisinvention.

EXAMPLES Catalyst A: SiO₂—CaSiO₃ Catalyst on Steam Treated Support with33% Moisture

100 g of support material comprising SiO₂ with 6 wt. % CaSiO₃ wassteamed at a temperature of above 50° C. for 3.5 hours. The support wasthen evaporated under reduced pressure in a rotary evaporator to produce150 g of 33% moisture steam-treated support. 15 g of this steam treatedsupport was used to create the catalyst. A stock solution of Sndissolved metal in water was prepared by dissolving 0.21 g of SnC₂O₄ and0.376 g of NH₄OX in 5.5 mL of H₂O. A stock solution of Pt dissolvedmetal was prepared by diluting 1.1 g PtC₂O₄ in 5.5 mL H₂O. Next, equalvolumes of the Pt and Sn stock solutions were mixed and stirred at roomtemperature for 15 minutes. This mixture was impregnated on the solid tocreate a metal loading of 1.2 wt. % Sn and 1 wt. % Pt, and the resultingcatalyst was then dried in a rotary evaporator and then in an oven for 6hours at 120° C. Finally, the catalyst was calcined at 350° C. for 6hours. The catalyst comprises 1 wt. % Pt, 1.2 wt. % Sn on a silicasupport comprising 6 wt. % CaSiO₃.

Catalyst B: 20% Moisture Steam Treated Catalyst

The procedure for making the 33% moisture steam-treated catalyst wasfollowed for making the 20% moisture steam-treated catalyst, except thesteam treated support was evaporated to a weight of 125 g. 12.5 g ofthis steam treated support was used to create the catalyst. The catalystcomprises 1 wt. % Pt, 1.2 wt. % Sn on a silica support comprising 6 wt.% CaSiO₃.

Catalyst C: Moisture Steam Treated Dry Support

The procedure for making the 33% moisture steam-treated catalyst wasfollowed for making the moisture steam-treated dry support, except thesteam treated support was evaporated at a reduced pressure until thesupport weight became stable, that is, until no measured weight loss wasachieved with subsequent evaporation, i.e. the moisture was less than 1wt. %. 10 g of this steam treated support was used to create thecatalyst. The catalyst comprises 1 wt. % Pt, 1.2 wt. % Sn on a silicasupport comprising 6 wt. % CaSiO₃.

Catalyst D: Dry Support Comparative Catalyst

10 g of support material comprising SiO₂ with 6 wt. % CaSiO₃ was used tocreate the catalyst. A stock solution of Sn dissolved metal in water wasprepared by dissolving 0.21 g of SnC₂O₄ and 0.376 g of NH₄OX in 5.5 mLof H₂O. A stock solution of Pt dissolved metal was prepared by diluting1.10 g PtC₂O₄ in 5.5 mL H₂O. Next, equal volumes of the Pt and Sn stocksolutions were mixed and stirred at room temperature for 15 minutes.This mixture was impregnated on the dry solid to create a metal loadingof 1.2 wt. % Sn and 1 wt. % Pt, and the resulting catalyst was thendried in a rotary evaporator and then in an oven for 6 hours at 120° C.Finally, the catalyst was calcined at 350° C. for 6 hours. The catalystcomprises 1 wt. % Pt, 1.2 wt. % Sn on a silica support comprising 6 wt.% CaSiO₃.

Radial Crush Strength Measurements

The radial crush strength of the catalysts and a silica support weremeasured according the ASTM D6175-03, “Standard test method for radialcrush strength of extruded catalyst and catalyst carrier particles.”

Conversion/Selectivity Measurements

Catalysts A, B, C, and D were placed in separate reactor vessels anddried by heating at 120° C. Feedstock acetic acid vapor was charged tothe reactor vessels along with hydrogen and helium as a carrier gas withan average combined gas hourly space velocity (GHSV) of 2430 hr⁻¹, atemperature of 250° C., a pressure of 2000 kPa, and mole ratio ofhydrogen to acetic acid of 8:1. Product samples are taken and analyzedto determine conversion and selectivity. Analysis of the products iscarried out by online gas chromatograph (GC). A three channel compact GCequipped with one flame ionization detector (FID) and 2 thermalconducting detectors (TCD) is used to analyze the feedstock reactant andreaction products. The front channel is equipped with an FID and aCP-Sil 5 (20 m)+WaxFFap (5 m) column and is used to quantify:acetaldehyde; ethanol; acetone; methyl acetate; vinyl acetate; ethylacetate; acetic acid; ethylene glycol diacetate; ethylene glycol;ethylidene diacetate; and paraldehyde. The middle channel is equippedwith a TCD and Porabond Q column and is used to quantify: CO₂; ethylene;and ethane. The back channel is equipped with a TCD and Porabond Qcolumn and is used to quantify: helium; hydrogen; nitrogen; methane; andcarbon monoxide.

Table 1 summarizes results of the radial crush strength, conversion andselectivity measurements.

TABLE 1 Radial Con- Selec- Selec- EtOH Support Crush version tivity totivity to Pro- Moisture Strength of HOAc EtOH EtOAc ductivity CatalystContent (N/mm) (%) (%) (%) (g/kg/h) A 33% 10.40 76 79 17 698 B 20% 6.1777 79 16 732 C <1% 6.04 75 79 16 670 Comp. D  0% 3.35 71 81 15 619Support  0% 10.76 — — — —

It is observed from these examples that catalysts with steam treatedsupports have an increased radial crush strength and productivity.

While the invention has been described in detail, modifications withinthe spirit and scope of the invention will be readily apparent to thoseskilled in the art. All publications and references discussed above areincorporated herein by reference. In addition, it should be understoodthat aspects of the invention and portions of various embodiments andvarious features recited may be combined or interchanged either in wholeor in part. In the foregoing descriptions of the various embodiments,those embodiments which refer to another embodiment may be appropriatelycombined with other embodiments as will be appreciated by one skilled inthe art. Furthermore, those skilled in the art will appreciate that theforegoing description is by way of example only, and is not intended tolimit the invention.

We claim:
 1. A hydrogenation catalyst for converting acetic acid toethanol, the catalyst comprising: one or more active metals on a silicasupport, wherein the one or more active metals is selected from thegroup consisting of cobalt, copper, gold, iron, nickel, palladium,platinum, iridium, osmium, rhenium, rhodium, ruthenium, tin, zinc,lanthanum, cerium, manganese, chromium, vanadium, molybdenum andmixtures thereof, wherein the catalyst has a radial crush strength of atleast 4 N/mm.
 2. The catalyst of claim 1, wherein the silica support issubjected to steam treatment at a temperature above 50° C. for a periodof time prior to impregnating the one or more metals on the silicasupport.
 3. The catalyst of claim 1, wherein the catalyst is made by:providing a dry support selected from the group consisting of silica,silica/alumina, calcium metasilicate, pyrogenic silica, high puritysilica, and mixtures thereof; subjecting the dry support to treatmentwith steam at a temperature from 50° C. to 300° C. for a period of timefrom 0.1 to 200 hours; drying the support such that the supportcomprises at least 0.5% moisture after treatment; and impregnating thesupport with the one or more active metals.
 4. The catalyst of claim 3,further comprising calcining the catalyst at a temperature from 250° C.to 800° C., optionally for a period from 1 to 12 hours.
 5. The catalystof claim 1, wherein the radial crush strength is from 4 N/mm to 12 N/mm.6. The catalyst of claim 1, wherein the silica support has an averageparticle size from 0.01 to 1.0 cm.
 7. The catalyst of claim 1, whereinthe support material has a surface area from 50 to 600 m²/g.
 8. Thecatalyst of claim 1, wherein the silica support is selected from thegroup consisting of silica, silica/alumina, calcium metasilicate,pyrogenic silica, high purity silica, or mixtures thereof.
 9. Thecatalyst of claim 1, wherein the one or more active metals is selectedfrom the group consisting of palladium, iron, cobalt, platinum, tin andcombinations thereof.
 10. The catalyst of claim 1, wherein the supportmaterial is present in an amount from 25 to 99 wt. %, based on the totalweight of the catalyst composition.
 11. The catalyst of claim 1, whereinthe support material further comprises a support modifier, wherein thesupport modifier is present in an amount from 0.1 to 50 wt. %, based onthe total weight of the catalyst composition.
 12. The catalyst of claim11, wherein the support modifier is selected from the group consistingof (i) alkaline earth metal oxides, (ii) alkali metal oxides, (iii)alkaline earth metal metasilicates, (iv) alkali metal metasilicates, (v)Group IIB metal oxides, (vi) Group IIB metal metasilicates, (vii) GroupIIIB metal oxides, (viii) Group IIIB metal metasilicates, and mixturesthereof.
 13. The catalyst of claim 11, wherein the support modifier iscalcium metasilicate or calcium oxide.
 14. The catalyst of claim 11,wherein the support modifier is selected from the group consisting ofWO₃, ZrO₂, Nb₂O₅, Ta₂O₅, Al₂O₃, B₂O₃, P₂O₅, Sb₂O₃, MoO₃, Fe₂O₃, Cr₂O₃,V₂O₅, MnO₂, CuO, Co₂O₃, Bi₂O₃, and combinations thereof.
 15. Thecatalyst of claim 3, wherein the treatment with steam is at atemperature from 50° C. to 150° C.
 16. The catalyst of claim 3, whereinthe treatment with steam is at a partial pressure from 100 to 5,000 kPa.17. The catalyst of claim 3, wherein the weight of the silica supportincreases by at least 0.0001% during the treatment with steam.
 18. Thecatalyst of claim 3, wherein the weight of the silica support increasesby at least 20% during the treatment with steam.
 19. The catalyst ofclaim 3, wherein the support comprises from 0.5 to 33% moisture afterthe drying.